Project Summary/Abstract Proposed is an advanced wearable for the prevention and rehabilitation of sport-related overuse injuries in youth athletes. Significance: The National SAFE KIDS Campaign, estimates that more than 3.5 million children are injured annually playing sports or participating in recreational activities. Of these, overuse is estimated to cause 45.9% to 54% of sports injuries and resulted in a total healthcare cost of over $2 billion. Children who participate in two or more sports that emphasize the same body part (for example, swimmers and baseball pitchers) are at an elevated risk to overuse injuries. Because youth athletes are still growing, certain overuse injuries may disturb the growth of the bone, resulting in angular limb deformities, length discrepancies or altered joint mechanics, creating the potential for significant long-term disability. Current methods of overuse injury prevention / rehabilitation are rudimentary (e.g. baseball pitch count) and fail to account for the subtleties of differing player technique and effort. Hypothesis: A system capable of accurately quantifying cumulative injury levels in youth athletes will reduce incidence of and aid in recovery from overuse injuries. Specific Aims: To prove the feasibility of the proposed system in Phase I IDL will 1) Build prototype sensor hardware; 2) Collect motion capture data on movements common to baseball play; and 3) Develop algorithms to quantify injury associated with common baseball movements. The overall phase 1 effort will demonstrate the ability of the proposed system to quantify injury associated with different baseball movement.